wip: add CleanOutAccount.

This implements the CleanOutAccount rpc which
is a variation of SweepAccount which allows as
many transactions as possible to be generated
in cleaning out an account All generated
transactions also respect the  MaxTxSize limit
of the network.

rpc/api.proto

@@ -62,6 +62,7 @@ service WalletService {
 	rpc ValidateAddress (ValidateAddressRequest) returns (ValidateAddressResponse);
 	rpc CommittedTickets (CommittedTicketsRequest) returns (CommittedTicketsResponse);
 	rpc SweepAccount (SweepAccountRequest) returns (SweepAccountResponse);
+	rpc CleanOutAccount (CleanOutAccountRequest) returns (CleanOutAccountResponse);
 }
 
 service WalletLoaderService {
@@ -1071,3 +1072,20 @@ message SweepAccountResponse {
 	int64 total_output_amount = 3;
 	uint32 estimated_signed_size = 4;
 }
+
+message CleanOutAccountRequest {
+	string source_account = 1;
+	string destination_address = 2;
+	uint32 required_confirmations = 3;
+	double fee_per_kb = 4;
+}
+
+message CleanOutAccountResponse {
+	message CleanOutAccountTransaction {
+		bytes unsigned_transaction = 1;
+		int64 total_previous_output_amount = 2;
+		int64 total_output_amount = 3;
+		uint32 estimated_signed_size = 4;
+	}
+	repeated CleanOutAccountTransaction transactions = 1;
+}

rpc/documentation/api.md

@@ -1,6 +1,6 @@
 # RPC API Specification
 
-Version: 5.8.x
+Version: 5.9.x
 
 **Note:** This document assumes the reader is familiar with gRPC concepts.
 Refer to the [gRPC Concepts documentation](http://www.grpc.io/docs/guides/concepts.html)
@@ -578,6 +578,7 @@ The service provides the following methods:
 - [`CommittedTickets`](#committedtickets)
 - [`BestBlock`](#bestblock)
 - [`SweepAccount`](#sweepaccount)
+- [`CleanOutAccount`](#cleanoutaccount)
 
 #### `Ping`
 
@@ -1982,13 +1983,43 @@ an account per the request parameters.
 - `double fee_per_kb`: The minimum relay fee policy (optional).
 
 **Response:** `SweepAccountResponse`
-- `bytes unsigned_transaction`: The unsigned transaction bytes.
+  - `bytes unsigned_transaction`: The unsigned transaction bytes.
 
-- `int64 total_previous_output_amount`: The total transaction input amount.
+  - `int64 total_previous_output_amount`: The total transaction input amount.
 
-- `int64 total_output_amount`: The total transaction output amount.
+  - `int64 total_output_amount`: The total transaction output amount.
 
-- `uint32 estimated_signed_size`: The estimated size of the transaction when signed.
+  - `uint32 estimated_signed_size`: The estimated size of the transaction when signed.
+___
+
+___
+
+#### `CleanOutAccount`
+
+The `CleanOutAccount` method moves as much value as possible using a batch of 
+transactions for the provided account.
+
+**Request:** `CleanOutAccountRequest`
+- `string source_account`:  The account to be cleaned out.
+
+- `string destination_address`: The destination address to pay to.
+
+- `uint32 required_confirmations`: The minimum utxo confirmation requirement.
+
+- `double fee_per_kb`: The minimum relay fee policy (optional).
+
+**Response:** `CleanOutAccountResponse`
+- `repeated CleanOutAccountTransaction transactions`: A collection of transactions cleaning out the provided account.
+
+  **Nested message:** `CleanOutAccountTransaction`
+
+  - `bytes unsigned_transaction`: The unsigned transaction bytes.
+
+  - `int64 total_previous_output_amount`: The total transaction input amount.
+
+  - `int64 total_output_amount`: The total transaction output amount.
+
+  - `uint32 estimated_signed_size`: The estimated size of the transaction when signed.
 ___
 
 #### `TransactionNotifications`

rpc/rpcserver/server.go

@@ -801,6 +801,59 @@ func (s *walletServer) SweepAccount(ctx context.Context, req *pb.SweepAccountReq
 	return res, nil
 }
 
+func (s *walletServer) CleanOutAccount(ctx context.Context, req *pb.CleanOutAccountRequest) (*pb.CleanOutAccountResponse, error) {
+	feePerKb := s.wallet.RelayFee()
+
+	// Use provided fee per Kb if specified.
+	if req.FeePerKb < 0 {
+		return nil, status.Errorf(codes.InvalidArgument, "%s",
+			"fee per kb argument cannot be negative")
+	}
+
+	if req.FeePerKb > 0 {
+		var err error
+		feePerKb, err = dcrutil.NewAmount(req.FeePerKb)
+		if err != nil {
+			return nil, status.Errorf(codes.InvalidArgument, "%v", err)
+		}
+	}
+
+	account, err := s.wallet.AccountNumber(req.SourceAccount)
+	if err != nil {
+		return nil, translateError(err)
+	}
+
+	txs, err := s.wallet.CleanOutAccount(account, req.DestinationAddress,
+		feePerKb, req.RequiredConfirmations)
+	if err != nil {
+		return nil, translateError(err)
+	}
+
+	res := &pb.CleanOutAccountResponse{}
+	res.Transactions =
+		make([]*pb.CleanOutAccountResponse_CleanOutAccountTransaction, len(txs))
+	var txBuf bytes.Buffer
+	for idx, tx := range txs {
+		txBuf.Grow(tx.Tx.SerializeSize())
+		err = tx.Tx.Serialize(&txBuf)
+		if err != nil {
+			return nil, translateError(err)
+		}
+
+		entry := &pb.CleanOutAccountResponse_CleanOutAccountTransaction{
+			UnsignedTransaction:       txBuf.Bytes(),
+			TotalPreviousOutputAmount: int64(tx.TotalInput),
+			TotalOutputAmount:         int64(h.SumOutputValues(tx.Tx.TxOut)),
+			EstimatedSignedSize:       uint32(tx.EstimatedSignedSerializeSize),
+		}
+
+		res.Transactions[idx] = entry
+		txBuf.Reset()
+	}
+
+	return res, nil
+}
+
 func (s *walletServer) BlockInfo(ctx context.Context, req *pb.BlockInfoRequest) (*pb.BlockInfoResponse, error) {
 	var blockID *wallet.BlockIdentifier
 	switch {